Best Used Speaker for Around $5000??

Since you mention used A'gon prices as a reference: absolutely do have a look at a pair of demo Gemme Audio Katana on offer on the 'Gon for $ 5.2k (from $ 12k) with full warranty and trade-in programme.
Just over 1 meter high, this is a stunningly looking 8ohm two way floorstander delivering a fabulous performance. Superb timing, deep bass (as opposed to big or fat), absolutely coherent and truly able to stir emotion. And, imho one of a small and very select group of producers who know how to obtain the virtues of ceramic drivers whilst avoiding the notorious disadvantages (together with You-Know-Who if you read my postings ;^)), far better than some big names. Sensitivity is comparable with your present speakers (85-86 db).
To be sure, I have no connection whatsoever with the guys offering these gems (cheap pun intended, I confess).

I'd definitely consider look at Merlins.

Do you think my XA-30.5 would be ok with the Daedalus Ulysses?

I'd suggest a phone conversation with Lou on that question -- I'm sure he'll give you a knowledgeable and honest answer.

While I have no experience with the Pass amps, fwiw my own feeling is that I can't imagine that they would not be a good match for either the Ulysses or the DA-RMa. Considering your room size and their high sensitivity, your amp would undoubtedly be running Class A nearly all the time. For any occasional brief peaks that might require more power than is available in Class A, you would have 130W available into the DA-RMa's 8 ohm nominal impedance, and somewhere in the vicinity of 160W into the Ulysses nominal 6 ohm impedance (extrapolating from Stereophile's measurements).

Lou has indicated that the new AP (all-poly) crossover option, although not inexpensive, among other things makes these speakers significantly easier to drive. But even without that option, people have used them successfully with everything from SET's and OTL's to high-powered SS amps. Check out the recent threads at his Audiocircle forum for comments by others, particularly the threads on "Synergistic Amplifiers" and on the "All-Poly Option."

Good luck!

-- Al